It has been established that alkylpyrazines are natural components of tobacco smoke, and that they most probably are important contributors to tobacco smoke flavor [A. Baggett et al, J. Chromatog, 97, 79 (1974)]. Further it has been disclosed in the patent literature that addition of alkylpyrazines to tobacco results in an improvement in the flavor of smoking compositions as perceived by a test panel.
British No. 1,244,068 describes a method for improving the smoke flavor of tobacco or a tobacco mixture which consists of treating the tobacco with a pyrazine derivative of the following chemical structure: ##STR2## in which each R is independently a hydrogen atom, an aliphatic radical, an alicyclic radical or an aromatic hydrocarbon radical, such radicals having up to 9 carbon atoms, or R is a heterocyclic radical containing 4 to 9 carbon atoms.
Unlike alkylpyrazines which are ubiquitous in nature and heat-treated foodstuffs, acylpyrazines are more limited in their occurrence. For example, 2-acetyl-5-methylpyrazine and 2-acetyl-5-ethylpyrazine are reported as constituents of cocoa in Tobacco International, page 18ff (March 1979), and 1-(2-pyrazinyl)-1-butanone is tentatively identified as a water-soluble component of cigarette smoke in J. Agric. Food Chem., 25(2), 310 (1977).
Several acetylpyrazines are included in the F.E.M.A. listing of food additives as being useful for imparting a popcorn-nutty flavor to a foodstuff. The incorporation of acetylpyrazine, 2-acetyl-5-methylpyrazine or 2-acetyl-6-methylpyrazine as a popcorn-like flavorant in foodstuffs and tobacco is described in U.S. Pat. No. 3,402,051.
U.S. Pat. No. 3,767,428 disclosed a process for imparting a potato-like flavor to a foodstuff by the incorporation of 2-acetyl-3-ethylpyrazine.
U.S. Pat. No. 3,881,025 describes a process for enhancing the flavor of foodstuffs, beverages, tobacco products and the like which involves incorporating a combination of flavorant additives which include at least one pyrazine derivative of the formula: ##STR3## where the substituents R.sup.1, R.sup.2, R.sup.3 and R.sup.4 may be the same or different and either each represents a hydrogen atom or a saturated or unsaturated, cyclic or acyclic, linear or branched hydrocarbon radical, or R.sup.3 together with R.sup.4 may constitute a benzene ring, or one of them represents an acyl radical and each of the other a radical of the same type as those mentioned above.
U.S. Pat. No. 3,914,227 discloses the use of pyrazinyl alicyclic ketones as flavorants in foodstuffs and tobacco products. Pyrazinyl cyclohexyl ketone is described as a smoking composition additive which enhances the tobacco-like taste and aroma of a blended cigarette.
U.S. Pat. No. 3,917,872 describes the use of 2-formylpyrazine, 2-acetylpyrazine and 2-acetonylpyrazine as foodstuff and beverage flavorants.
There is continuing interest in the development of organic derivatives which can impart novel flavorant properties to smoking compositions, foodstuffs, beverages, and the like. A particular interest in pyrazines as flavorants or fragrances has stimulated the investigation of various types of substituted pyrazines which potentially have unique organoleptic properties.
Accordingly, it is an object of this invention to provide novel acylpyrazine compounds which exhibit a desirable combination of properties for application as flavorants.
It is a further object of this invention to provide smoking compositions containing a novel acylpyrazine flavorant additive, which smoking compositions are adapted to impart unique flavor and aroma to mainstream and sidestream smoke under smoking conditions.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.